Error - memory game?

i made a memory card game a everytime i run the app, i will shows an error. like:

Problem with application

Property setter was expecting a com.googl e.appinventor.components.runtime. Button component but got a String instead.

END APPLICATION

here is my block


Your images are not clear, try uploading png so it will be easy to assess by the community experts to sort out your error. In the button click event you did wrong logic

You need a separate list, buttonList, containing the Button components.

Each Button component block is at the end of that Button's blocks pallette in the Blocks Editor.

They are green.